Electronic component and fabricating method

ABSTRACT

An LSI unit provided by the present invention comprises a molded LSI chip having bonding pads, and another LSI chip having another set of bonding pads which is placed on the molded LSI chip and electrically connected the molded LSI chip through bumps. In this LSI unit, the LSI chip is molded in a molding material, a re-wiring layer is formed, and bonding pads of the molded LSI chip are formed so as to correspond to the position of another set of bonding pads of another LSI chip, where the bonding pads of the molded LSI chip are formed over the molding material. Thus another LSI chip even larger in size than the molded LSI chip can be placed on the molded LSI chip and can be electrically connected thereto.

CROSS REFERENCE TO RELATED APPLICATIONS

The present document is based on Japanese Priority DocumentJP2002-035306, filed in the Japanese Patent Office on Feb. 13, 2002, theentire contents of which being incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an electronic component and a method offabricating thereof, and more specifically to an electronic componentwhich is designed to allow expansion of the system scale at a low costand a method of fabricating thereof.

BACKGROUND OF THE INVENTION

There are strong needs for downsizing, weight reduction and functionalupgrading in the recent fields of mobile terminal and information/homeappliances, which eventually demands functional upgrading of LSI(large-scale integrated circuit). Thus there is an accelerated trend offabricating circuits using a plurality of different processes on asingle wafer, which is known as SOC (system-on-chip).

SOC, however, requires a longer and more complicated process as comparedwith a single process, and thus has general tendencies of lower yieldratio and longer development period. SOC is also disadvantageous in thatthe individual circuits cannot be fabricated according to respectiveoptimum processes since all processes are carried out on the waferbasis, which may yield poorer functions ones rather than those obtainedin the single process.

In recent years, interest has been growing on SIP (system-in-package).The SIP is to make various (same kind of, or different kinds of) LSI orIC, which are fabricated by the conventional single process and arealready inspected as non-defective, into a unit or module which can behandled as a single component (LSI or IC) by combining and re-wiring.SIP can thus readily realize an LSI unit or IC module having a highyield ratio and a diversified functions.

As a representative structure of the SIP, a chip-on-chip structuretypified by an LSI unit 1 is shown in FIGS. 1 and 2. FIG. 1 shows asectional side elevation of the LSI unit 1, and FIG. 2 shows a plan viewof the LSI unit 1 as viewed from the top.

The LSI unit 1 comprises an LSI chip 11 having a lateral length of x₁and a longitudinal length of y₁, and an LSI chip 12 having a laterallength of x₂ and a longitudinal length of y₂ (where x₁>x₂ and y₁>y₂).

In the LSI unit 1, the LSI chip 12 having bonding pads 15 is placed onthe LSI chip 11 having bonding pads 14 so that the individual activesurfaces thereof are faced with each other, and the both areelectrically connected by placing bumps 13 in between. To bonding pads16 of the LSI chip 11, wirings 17 used for connecting the LSI unit 1 toany external circuit (not shown) are bonded.

As shown in FIG. 1, the chip-on-chip structure has advantages in thatenabling mounting of a plurality of LSI chips, reduction in mountingarea through employment of a three-dimensional structure, and shorteningof the wiring between the LSI chips through employment of theface-to-face configuration of the active surfaces.

SUMMARY OF THE INVENTION

In the above chip-on-chip structure, it is indispensable that layout ofthe bonding pads 14 of the lower LSI chip 11 and the bonding pads 15 ofthe upper LSI chip 12 coincide with each other both for physical andwiring integrities. The LSI chips 11 and 12 are, however, manufacturedgenerally in an independent manner, so that it is almost unlikely thatany of ready-made LSI chips can be combined so as to allow the bondingpads 14 and bonding pads 15 to oppose each other. As a consequence,there has been a problem that at least either of the LSI chips (e.g.,LSI chip 12) must be manufactured according to a specific designtherefor so as to allow combination with the LSI chip 11.

Another disadvantage resides in that the relations of lateral length ofx₁>x₂ and longitudinal length of y₁>y₂ must always be satisfied so as toconnect the LSI unit 1 with any external circuits as shown in FIG. 2,which inconveniently restricts size of the LSI chip to be connected, andconsequently degrades the yield ratio of the LSI unit andcost-efficiency.

The present invention is conceived considering the foregoing situation,and is intended for achieving cost reduction and expansion of systemscale.

An electronic component in accordance with an aspect of the presentinvention includes bonding pads formed by re-wiring of a moldedelectronic device; and another electronic device electrically connectedthrough the bonding pads to the molded electronic device while allowingthe active surface of the electronic devices to oppose with that of themolded electronic device.

The electronic devices may be semiconductor chips.

The bonding pads may be formed on the molding material.

A method of fabricating an electronic component in accordance with anaspect of the present invention includes: a first step for attaching anadhesive member which exhibits lower adhesiveness after thepredetermined process, on a flat substrate; a second step for placingtwo or more electronic devices on the adhesive member while directing anactive surfaces of the electronic devices facedown; a third step formolding the electronic devices using a molding material on the flatsubstrate; a fourth step for subjecting the adhesive member to thepredetermined process to lower the adhesive force of the adhesivemember, and for separating the molded electronic devices from the flatsubstrate; a fifth step for forming a re-wiring layer on the moldedelectronic devices using a metal thin film for forming bonding pads; asixth step for placing other electronic devices on the molded electronicdevices while allowing an active surfaces of both electronic devices tooppose each other, and for electrically connecting both electric devicesthrough the bonding pads; and a seventh step for dicing the molded unitincluding the electronic devices at the molding material so as toseparate the individual molded units.

The electronic devices may be semiconductor chips.

The bonding pads may be formed over the molding material.

In the electronic component and the fabricating method in accordancewith an aspect of the present invention, the molded electronic device isprovided with the re-wiring layer made of the metal thin film, and withthe bonding pads, on which bonding pads another electronic device isplaced so that the active surfaces of both devices are opposed eachother, and both devices are then electrically connected.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side elevation showing an exemplary configurationof a conventional LSI unit;

FIG. 2 is a plan view showing the configuration of the LSI unit shown inFIG. 1;

FIG. 3 is a block diagram showing a configuration of a fabricationprocess apparatus for LSI unit of an embodiment of the presentinvention;

FIG. 4 is a flow chart for explaining operations of the fabricationprocess apparatus for LSI unit shown in FIG. 3;

FIGS. 5A through 5N are schematic drawings for explaining fabricationprocesses of the LSI unit of the present invention;

FIG. 6 is a flow chart for explaining details of re-wiring process ofthe LSI unit in step S7 in FIG. 4;

FIG. 7 is a sectional side elevation showing an exemplary configurationof the LSI unit of another embodiment of the present invention;

FIG. 8 is a sectional side elevation showing an exemplary configurationof the LSI unit of still another embodiment of the present invention;

FIG. 9 is a sectional side elevation showing an exemplary configurationof the LSI unit of still another embodiment of the present invention;and

FIG. 10 is a sectional side elevation showing an exemplary configurationof the LSI unit of still another embodiment of the present invention.

DESCRIPTION OF THE PREFFERD EMBODIMENT(S)

Below, embodiments for carrying out the present invention will bedescribed specifically and in detail with reference to the accompanyingdrawings.

FIG. 3 is a block diagram showing a configuration of a fabricationprocess apparatus for LSI unit of an embodiment of the presentinvention.

The fabrication process apparatus have a substrate alignment section 31,a sheet adhesion section 32, an LSI alignment section 33, a guideprocessing section 34, a molding material processing section 35, a heattreatment processing section 36, a re-wiring processing section 37, anelectronic device bonding section 38 and a dicing section 39.

The substrate alignment section 31 provides a supporting substrate 51(FIG. 5A) and placing it to a predetermined position. The sheet adhesionsection 32 attaches an adhesive sheet 52 (FIG. 5B) on the supportingsubstrate 51, and coats a separation layer 53 (FIG. 5C) on the adhesivesheet 52.

The LSI alignment section 33 controls a mounter (not shown) having animage recognition function and placing LSI chips 54 (FIG. 5D) on thesupporting substrate 51. The guide processing section 34 places andremoves a flow-stop guide 57 (FIG. 5E) onto or from the periphery of thesupporting substrate 51.

The molding material processing section 35 pours a molding material 58(FIG. 5F) over the supporting substrate 51. The heat treatment section36 heats everything formed on the supporting substrate 51 for curing themolding material 58, and separates the cured molding material 58 havingLSI units 56 (FIG. 5G) from the supporting substrate 51.

The re-wiring processing section 37 re-wires the LSI units 56 wherebybonding pads 64 (FIG. 5M) for connecting other LSI chips (FIG. 5N) areformed. The electronic device bonding section 38 controls a mounter soas to place LSI chips 65 on the LSI units 56, to thereby electricallyconnect the LSI chips 65 and LSI units 56. The dicing section 39 dicesthe thus-formed semiconductor LSI integrated board including a pluralityof LSI units 56 into the individual units.

Next, the fabrication process of the LSI unit of the embodiment inaccordance with the present invention will be described referring to theflow chart in FIG. 4 and the process charts shown in FIG. 5A throughFIG. 5N.

First in step S1, the substrate alignment section 31 provides thesupporting substrate 51 (FIG. 5A) and aligns it to a predeterminedposition. The supporting substrate 51 is temporarily used for placingthe LSI chips 54 (FIG. 5D), and is a square plate of approx. 20 cm inlength and of 1 to 3 mm in thickness made of metal, glass or silicon.The surface of the supporting substrate 51 has specular finish.

Next in step S2, the sheet adhesion section 32 attaches the adhesivesheet 52 (FIG. 5B) on the supporting substrate 51, and then forms theseparation layer 53 (FIG. 5C) by coating on the adhesive sheet 52. Theseparation layer 53, which has a property of reducing the adhesive forcewhen irradiated by heat or ultraviolet radiation, is coated in order tolower adhesion strength of the adhesive sheet 52 in the later processstep.

Next in step S3, the LSI alignment section 33 aligns a predeterminednumber of LSI chips 54 on the supporting substrate 51 while directingthe active surfaces thereof facedown. Accordingly, the bonding pads 55of the LSI chips 54 to come into contact with the separation layer 53.The LSI chips 54 are such as those fabricated in the single process andhas already been inspected as non-defective.

In an exemplary case shown in FIG. 5D, each LSI chip 54 composes one LSIunit (combination of LSI chips) 56. A predetermined number of LSI units54 are placed at predetermined positions on the supporting substrate 51so as to form a plurality of LSI units 56. More specifically, theprovided LSI chips 54 are placed, using a mounter having an imagerecognition function, on the supporting substrate 51 at the positionspreviously defined in a precise manner with an accuracy of ±5 μm orhigher while directing the active surfaces thereof facedown (in thedirection of contact with the separation layer 53).

While one LSI unit 56 comprises only one LSI chip 54 in the exemplarycase shown in FIG. 5D, it is also allowable to combine a plurality ofLSI chips. The LSI chips to be combined may be of the same type ordifferent types and may be combined in an arbitrary number but should beinspected to be non-defective. It is still also allowable to aligncomponents such as capacitor or resistor in place of the LSI chips.

Next in step S4 shown in FIG. 4, the guide processing section 34 places,on the periphery of the supporting substrate 51 as shown in FIG. 5E, theflow-stop guide 57 for preventing outflow of the molding material 58(FIG. 5F) which is used for molding the LSI units 56. Shape of theflow-stop guide 57 may be round or square so far as it can stop theflow. Thereafter in step S5, the molding material processing section 35pours over the supporting substrate 51 the molding material 58 (FIG. 5F)for molding the LSI units 56.

The molding material 58 is made of a resin and a filler. The resin isused for a base of the molding material 58, and is made of such as anepoxy resin. It is, however, to be noted that the epoxy resin generallyhas property of large curing shrinkage and thermal expansion coefficientcausing to warping or crack, so that it is necessary to select thosehaving relatively small relevant values. As an additional measure, alarge amount of filler is mixed therewith so as to prevent warping orcrack of the resin, to thereby reduce distortion of the molding material58. Spherical silica (quartz) having a small heat expansion coefficientis typically used as the filler. The spherical silica can be containedin the molding material 58 in an amount of up to 90% of weight ratio byproperly combining varied grain size thereof.

It is of course allowable to use other organic resins in place of epoxyresin, and to use other materials such as glass or ceramic in place ofspherical silica.

Next in step S6 shown in FIG. 4, the heat treatment section 36 cures themolding material 58 with heat, and then separates the cured bondedmaterial from the supporting substrate 51. The guide processing section34 removes the flow-stop guide 57 (FIG. 6G). More specifically,everything formed on the supporting substrate 51 is heated at 100° C.for 30 minutes, and further at 150° C. for 80 minutes. Since theseparation layer 53 lowers the adhesive force of the adhesive sheet 52by this heating, the molding material 58 and the active surfaces of theLSI units 56 can readily be separated from the supporting substrate 51,which produces a molded semiconductor LSI integrated board.

Next in step S7, the re-wiring section 37 executes re-wiring operationof the semiconductor LSI integrated board (LSI units 56). The re-wiringoperation of the LSI units 56 will be explained referring to the flowchart shown in FIG. 6.

FIG. 5H shows the LSI units 56 shown in FIG. 5G which turned up theactive surfaces. The bonding pads 55 of the LSI chips 54 are thuspositioned in the upper planes of the LSI units 56.

Now in step S21, as shown in FIG. 5H, the re-wiring processing section37 coats, using a spinner, an overcoat resin (e.g., photo-sensitivepolyimide liquid resin) over the active surfaces of the LSI units 56 soas to form an inter-layer film 59. The inter-layer film 59 planarizesthe cured molding material 58 and the active surfaces of the LSI units56, and also serves as a passivation film for the LSI chips 54.

The re-wiring processing section 37 further forms contact holes 60having a diameter of 30 μm or below in the inter-layer film 59 atpredetermined positions (positions corresponded to the bonding pads 55of the LSI chips 54) as shown in FIG. 5I. Actually in the bond area forthe LSI chip 54, several hundreds to several thousands of contact holes60 for the re-wiring of the LSI chip 54 are formed per LSI unit 56. Thecontact holes 60 are made by forming a photoresist film on theinter-layer film 59, exposing and developing predetermined positions ofthe photoresist film, and the resultant portion of the photoresist filmis then cured by heating and used as a mask for etching the inter-layerfilm 59.

Next in step S23, the re-wiring processing section 37 forms, as shown inFIG. 5J, a metal thin film 61 which will later serve as a re-wiringlayer 62 (FIG. 5K) on the inter-layer film 59 having formed therein thecontact holes 60. Part of the metal thin film 61 is connected to thebonding pads 55 through the contact holes 60. The metal thin film 61comprises an underlying layer of nickel or chromium and a copper layerstacked thereon, both of which are formed by sputtering. The underlyinglayer improves adhesiveness of the inter-layer film 59 with the copperfilm, and has a thickness of 50 to 200 nm. The copper layer has athickness of 500 nm to 5 μm.

Next in step S24, the re-wiring processing section 37 forms on the metalthin film 61 a mask pattern including a master pattern for apredetermined circuit using a photoresist by a photolithographicprocess. Then in step S25, the re-wiring processing section 37 etchesthe metal thin film 61 having formed thereon the photoresist maskpattern having a master pattern for a predetermined circuit using aspecialized etching solution for the metal, to thereby transfer thecircuit pattern to the metal thin film 61. The re-wiring processingsection 37 then removes the resist mask from the metal thin film 61. There-wiring layer 62 is thus formed on the inter-layer film 59 as shown inFIG. 5K.

Next in step S26, the re-wiring processing section 37 forms, as shown inFIG. 5L, a resin layer 63 using, for example, an epoxy resin on the LSIunits 56 having formed thereon the re-wiring layer 62, and further, instep S27, forms bonding pads 64 (FIG. 5M) as being exposed in the resinlayer 63 corresponding to the position of bonding pads 66 of the LSIchips 65 placed in the later process shown in FIG. 5N. The bonding pads64 are formed as a portion of the re-wiring layer 62 exposed in theresin layer 63, where the resin layer 63 is patterned by forming thereona photoresist film, exposing and developing predetermined positions ofthe photoresist film, and the resultant portion of the photoresist filmis then cured by heating and used as a mask for etching the resin layer63.

Upon completion of the re-wiring processing as described in the above,the electronic device bonding section 38 aligns, in step S8 shown inFIG. 4, the LSI chips 65 on the LSI units 56 having formed thereon thebonding pads 64 while directing the active surfaces of the LSI chips 65facedown so as to electrically connect them through the bonding pads 64.More specifically, bumps 67 are formed on the individual bonding pads64, and the provided LSI chips 65 are placed on the LSI units 56 using amounter having an image recognition function at the positions previouslydefined in a precise manner with an accuracy of ±5 μm or higher whiledirecting the active surfaces thereof facedown (so that the activesurfaces of the LSI chips 54 in the LSI units 56 and active surfaces ofthe LSI chips 65 are opposed). This makes the bonding pads 66 of the LSIchips 65 electrically connected to the bonding pads 55 of the LSI chips54 while being mediated by the bumps 67 and the bonding pads 64(re-wiring layer 62).

The LSI chips 65 are such as those fabricated in the single processsimilarly to the LSI chips 54, and has already been inspected asnon-defective. It is also allowable to place passive components such ascapacitor or resistor in place of the LSI chips 65.

While FIGS. 5A through 5N showed only two LSI units 56, the actualsemiconductor LSI integrated board have a larger number of the LSI units56. Then in step S9 shown in FIG. 4, the dicing section 39 dices (cuts)thus-produced semiconductor LSI integrated board using a blade 68 so asto separate the individual units as shown in FIG. 5N. A number of LSIunits 56 are thus obtained.

As has been described in the above, in the LSI unit 56 applied to thepresent embodiment, the bonding pads 64 can be formed at arbitrarypositions so as to correspond to the position of electronic devices(e.g., bonding pads 66 of the LSI chips 65). This relieves thepositional restriction of the bonding pads of the electronic devices andthus allows a great variety of electronic devices to be used, so that itis no more necessary in the fabrication of the LSI units 56 to re-designthe electronic devices to be connected thereto, which is alsoadvantageous for reducing the cost.

FIG. 7 shows an exemplary configuration of the LSI unit 56 obtainedafter dicing the semiconductor LSI integrated board shown in FIG. 5N. Itis to be noted that, in FIG. 7, since portions corresponded to thoseshown in FIGS. 5A through 5N are given with the same reference numerals,detailed description of them are omitted in order to avoid redundancy.

The LSI unit 56 comprises the LSI chip 54 having bonding pads 55, andanother LSI chip 65 having the bonding pads 66. The LSI unit 56 is alsoconnected to an external circuit with wirings 71 through the bondingpads 64 shown on the leftmost and rightmost sides of the drawing.

Since the LSI unit 56 is fabricated in such a way that the LSI chip 54is molded in the molding material 58, re-wired, and formed the bondingpads 64 as being corresponded to (the bonding pads 66 of) the positionof the LSI chip 65, so that the bonding pads 64 are formed over themolding material 58. This makes it possible that the LSI chip 65 havinga larger size than that of the LSI chip 54 is stacked and connected tothe LSI chip 54, and that the LSI chip 65 even having the bonding pads66, of which layout is different from that of the bonding pads 55 of theLSI chip 54, is stacked and connected to the LSI chip 54.

While the molded LSI chip 54 and the external LSI chip 65 areelectrically connected through the bumps 67 in the above-described LSIunit 56, the connection may be established through an anisotropicconductive adhesive, or through wire bonding using another set ofbonding pads tailored to the LSI chip 65 when re-wiring the molded LSIchip 54.

FIG. 8 shows another exemplary configuration of the LSI unit applied tothe present invention. It is to be noted that, in FIG. 8, since portionscorresponded to those shown in FIG. 7 are given with the same referencenumerals, detailed description of them are omitted in order to avoidredundancy.

An LSI unit 101 comprises an LSI chip 111, an LSI chip 112 and an LSIchip 113, all of which are fabricated by the single process similarly tothe LSI chip 54, and are inspected as non-defective.

In the LSI unit 101, the LSI chip 111 having bonding pads 114 and theLSI chip 112 having bonding pads 115 are molded in the molding material58, and thereon the LSI chip 113 having bonding pads 116 is placed so asto make the individual active surfaces opposed each other, and iselectrically connected through the bumps 67.

In this case, since the LSI chip 111 and LSI chip 112 are molded in themolding material 58, re-wired, and provided with the bonding pads 64 asbeing corresponded to the bonding pads 116 of the LSI chip 113, thebonding pads 64 are formed over the molding material 58. This isadvantageous for the case where a plurality of different types of LSIchips are molded in the molding material, since it is no more necessaryto re-design the LSI chip to be connected as being tailored to themolded LSI chips. The LSI unit 101 can thus be formed using theready-made LSI chip 113.

FIG. 9 shows still another exemplary configuration of the LSI unitapplied to the present invention. It is to be noted that, in FIG. 9,since portions corresponded to those shown in FIG. 7 are given with thesame reference numerals, detailed description of them are omitted inorder to avoid redundancy.

An LSI unit 121 comprises an LSI chip 131 and an LSI chip 132, both ofwhich are fabricated by the single process similarly to the LSI chip 54and are inspected as non-defective, and passive components 133 and 134such as capacitor or resistor.

In the LSI unit 121, the LSI chip 131 having bonding pads 135 and thepassive component 133 having the bonding pads 137 are molded in themolding material 58, and thereon the passive component 134 havingbonding pads 138 and the LSI chip 132 having bonding pads 136 are placedso as to make the individual active surfaces opposed with each other,and are electrically connected through the bumps 67.

As shown in the above, use of passive components in place of LSI chipcan also provide the LSI unit 121 applied to the present invention.

FIG. 10 shows still another exemplary configuration of the LSI unitapplied to the present invention. It is to be noted that, in FIG. 10,since portions corresponded to those shown in FIG. 7 are given with thesame reference numerals, detailed description of them are omitted inorder to avoid redundancy.

An LSI unit 141 comprises an LSI chip 151, an LSI chip 152 and an LSIchip 153, all of which are fabricated by the single process similarly tothe LSI chip 54 and are inspected as non-defective.

In the LSI unit 141, the LSI chip 151 having bonding pads 154 and theLSI chip 152 having bonding pads 155 are molded in the molding material58, and thereunder the LSI chip 153 having bonding pads 156 is placed soas to make the individual active surfaces opposed with each other, andis electrically connected through the bumps 67. The LSI chip 153 ismolded in a molding material 157 together with copper posts 158 whichare connected to the bonding pads 64 shown on the leftmost and rightmostsides in the drawing. The LSI unit 141 is connected to an externalcircuit (not shown) through the copper posts 158 and the bumps 159.

The present invention can successfully be applied also to thus-composedLSI unit 141.

As is clear from the above description, the present invention canreadily provide chip-on-chip LSI units based on combination ofready-made LSI chips since restrictions on the size of LSI chips andlayout of bonding pads can be relieved. This allows expansion of scaleof LSI units without enlarging the mounting area.

Mixed use of the passive components in place of the LSI chips in the LSIunit can further ensure improved performance and expanded scale of theLSI unit.

Further, since such LSI unit can be handled as a single chip, investingin the assembly facility is no more necessary and thus the productioncosts can be saved.

Therefore, according to the present invention, the system scale can beexpanding at a low cost.

Finally, the embodiments and examples described above are only examplesof the present invention. It should be noted that the present inventionis not restricted only to such embodiments and examples, and variousmodifications, combinations and sub-combinations in accordance with itsdesign or the like may be made without departing from the scope of thepresent invention.

1. An electronic component obtained by providing a molded structurearound sides of one or more first electronic devices, interfacing one ormore second electronic devices to said first electronic devices, saidcomponent further comprising: a metal re-wiring layer formed betweensaid first electronic devices and said second electronic devices, saidre-wiring layer patterned so as to form a pre-determined circuit, andwherein said re-wiring layer provides a plurality of individualconnections between pads of said first electronic devices andcorresponding pads of said second electronic devices, wherein said firstelectronic device is a larger size than said second electronic device.2. The electronic component as claimed in claim 1, wherein saidelectronic devices are semiconductor chips.
 3. The electronic componentas claimed in claim 1, wherein said first electronic devices interfacewith said re-wiring layer through bonding pads formed over said moldingmaterial. 4-6. (canceled)
 7. The electronic component as claimed inclaim 1, wherein said re-wiring layer connects an external circuit toone of the electronic devices contained within the component.
 8. Theelectronic component as claimed in claim 1, wherein the active surfacesof said first electronic devices oppose the active surfaces of saidsecond electronic devices.